Multi-user Diversity in Spectrum Sharing Systems over Fading Channels with Average Power Constraints

TL;DR

This paper analyzes how multi-user diversity and average power constraints affect spectrum sharing in cognitive radio systems over fading channels, highlighting capacity gains with more secondary and fewer primary receivers.

Contribution

It introduces a new formulation for fading distributions in multi-user spectrum sharing systems with average power constraints, providing insights into capacity and outage performance.

Findings

More secondary receivers increase achievable capacity.

Fewer primary receivers improve secondary system performance.

Average power constraints significantly influence optimal power allocation.

Abstract

The multi-user diversity in spectrum sharing cognitive radio systems with average power constraints over fading channels is investigated. Average power constraints are imposed for both the transmit power at the secondary transmitter and the interference power received at the primary receiver in order to provide optimal power allocation for capacity maximization at the secondary system and protection at the primary system respectively. Multiple secondary and primary receivers are considered and the corresponding fading distributions for the Rayleigh and Nakagami-m fading channels are derived. Based on the derived formulation of the fading distributions, the average achievable channel capacity and the outage probability experienced at the secondary system are obtained, revealing the impact of the average power constraints on optimal power allocation in multi-user diversity technique in fading environments with multiple secondary and primary receivers that share the same channel. The obtained results highlight the advantage of having on one hand more secondary receivers and on the other hand fewer primary receivers manifested as an increase in the achievable capacity.